Untreated Fused Silica Capillaries

Figure 6 Separation of basic proteins on an untreated fused silica capillary with diaminopropane as buffer additive. Capillary 75 cm (55 cm to detector) x 50 p i.d. Buffer pHs are as noted on the figure with 30 to 60 mM DAP as an additive 200 to 240 V/cm peak identification 1 = lysozyme, 2 = cytochrome, 3 = ribonuclease, 4 = a-chymotrypsin 5 = trypsinogen, 6 = r-huIL-4. (From Bullock, J. A. and Yuan, L.-C., /. Microcol. Sep., 3, 241, 1991. With permission.)...

Lee, K.-J. and Heo, G. S., Free solution capillary electrophoresis of proteins using untreated fused-silica capillaries, ]. Chromatogr., 559, 317, 1991. 

Much effort has been devoted to the applicaton of electrophoretic techniques for the analysis of dyes and dye decomposition products in industrial waste-waters. CZE with DAD and MS detection was employed for the determination of reactive dyes in spent dye-baths and waste-waters. The chemical structure of the dyes included in the experiments are shown in Fig. 3.149. Liquid samples were purified and preconcentrated by SPE. ODS cartridges were conditioned by washing with two bed volumes of methanol, four bed volumes of water and two bed volumes of 5 mM tetrabutylammonium phosphate. Aliquots of 10 - 30 ml were loaded and the cartridges were washed with 2 ml of water. Analytes were eluted with 2 ml of methanol-water (70 30, v/v). Untreated fused-silica capillaries (110 cm and 57 cm X 50 /im i.d.) were coupled to MS and DAD. The running... 

Mandrup, G. (1992). Rugged method for the determination of deamidation products in insulin solutions by free zone capillary electrophoresis using an untreated fused-silica capillary. J. Chromatogr. 604, 267—281. 

Lin and Wu [137] established a simple capillary zone electrophoresis method for the simultaneous analysis of omeprazole and lansoprazole. Untreated fused-silica capillary was operated using a phosphate buffer (50 mM, pH 9) under 20 kV and detection at 200 nm. Baseline separation was attained within 6 min. In the method validation, calibration curves were linear over a concentration range of 5-100 /iM, with correlation coefficients 0.9990. RSD and relative error were all less than 5% for the intra- and interday analysis, and all recoveries were greater than 95%. The limits of detection for omeprazole and lansoprazole were 2 fiM (S/N = 3, hydroxynamic injection 5 s). The method was applied to determine the quality of commercial capsules. Assay result fell within 94—106%. 

A. Effect of pH Acidic silanol groups at the surface of the capillary wall will dissociate when in contact with an electrolyte solution, as illustrated by Eq. (4.5). At high pH, the silanol groups are fully ionized, generating a dense compact layer and a high zeta potential. As a result, the magnitude of the EOF in untreated fused silica capillaries increases with increasing pH. 

The most common capillaries used in CZE or MECC for the analysis of small molecules are untreated fused silica capillaries. The analysis of large proteins by CZE and applications for cIEF are generally performed in coated capillaries. The CGE technique is performed in gel-filled capillaries or capillaries filled with polymer networks. 

Kappes et al. evaluated the potentiometric detection of acetylcholine and other neurotransmitters through capillary electrophoresis [209]. Experiments were performed on an in-house capillary electrophoresis instrument that made use of detection at a platinum wire, dip-coated in 3.4% potassium tetrakis (4-chlorophenyl) borate/64.4% o-nitrohenyl octyl ether/32.2% PVC in THF. The results were compared to those obtained using capillary electrophoresis with amperometric detection at a graphite electrode. Samples prepared in the capillary electrophoresis buffer were electrokinetically injected (7 s at 5 kV) into an untreated fused silica capillary (88 cm x 25 pm i.d.) and separated with 20mM tartaric acid adjusted to pH 3 with MgO as the running buffer. The system used an applied potential of 30 kV, and detection versus the capillary electrophoresis ground electrode. 

A Beckman P/ACE 5000 (Schaumberg, IL) was used for all CE separations. The background electrolyte (BGE) was CH3CN/H2O/HCOOH (50 45 5). Washing solution was 1% NH4OH. All untreated fused-silica capillaries were obtained from Polymicro Technologies (Phoenix, AZ). Column... 

The CE system consisted of a P/ACE System 2100 high-performance CE apparatus (Beckman Coulter, Fullerton, CA). An untreated, fused silica capillary tube (Beckman Coulter) was used, with dimensions of 75.0-pm ID, Lj=57.0 cm, and L =5Q.O cm, enclosed in a liquid-cooled cassette. Detection was performed with a UV-VIS detector (2=200.0 nm). Equipment was checked and data were processed with the Beckman P/ACE Station V 1.2 software (Beckman Coulter). 

One-step method for the preparation of highly enantioselective monolithic columns for CEC has been developed by Frechet et al. The chiral polymer bed of defined pore distribution and chiral ligand concentration has been synthesized within the confines of untreated fused silica capillaries using a mixture of O-[2-(methacryloyloxy)ethylcarbamoyl]-10,ll-dihydroquinidine 76, ethylene dimethacrylate (EDMA), and glycidyl methacrylate or 2-hydroxyethyl methacrylate (HEMA) in the mixture of cyclohexanol and 1-dodecanol as porogenic solvents. Under optimized synthetic and chromatographic conditions, these materials with the desired characteristics were demonstrated to efficiently separate a model racemic DNZ-Leu, Figure 13.24 [146],... 

Figure 11. Electropherogram of protein standards run in an untreated fused silica capillary, in pH 8.24 tricine buffer.

A CZE method for the separation of insulin and its deamidation products with untreated fused-silica capillaries using a run buffer containing 2-(A-cyclohexyl-amino) ethanesulfonic acid (CHES), triethylamine, and 10% acetonitrile has been reported [90]. This system separated acidic and neutral desamido-insulin in formulated human insulin with the relative standard deviation (RSD) of the migration times <1%, whereas RP-HPLC coeluted the neutral desamido-insulin with insulin. Sergeev et al. described an analytical scheme for monitoring recombinant human... 

FIGURE 2.7 Isoform analysis of phosphorylated HI histone by multidimensional HPLC-CZE. Panel (a) shows the separation of HI histones by RP-HPLC on a NucleosU 300-5 C4 column. Panel (b) shows the separation of the HI.5 RP-HPLC fraction by CZE. The CE analytical system included a Beckman-Coulter P/ACE 2100 instrument operated in normal polarity at 12 kV with UV detection at 200 nm and capillary cooling at 25°C. Nonphosphorylated (pO) and mono-, di-, and tri-phosphorylated (pi, p2, p3) H1.5 isoforms were separated on the basis of miz using a 57 cm long (50 cm to detector) by 75 ixm ID untreated fused-silica capillary. Separation media contained 0.1 M sodium phosphate, 0.02% hydroxypropyhnethylceUulose, pH 2.0. Samples were injected for 2 s. (From Sarg B, et al. J Biol Chem 2006 281 6573-80. With permission.)... 

---